1. Field of Invention
The invention relates to a bag manufacturing system that includes a tube forming device, which forms a tube and then separates the tube into tube pieces, a bottom forming device, which provides the tube pieces with bottoms so as to form bags, and a storage device for storing the tube pieces on at least two tiers.
2. Description of the Prior Art
As a rule, endless tubes are initially formed in a very efficient manner in so-called tube machines for manufacturing bags. For this purpose a web, which was made of paper or plastic and was delivered mostly on a roll, is first folded up into a tube and the web edges, which are now located on top of one another, are joined using suitable joining means, for example, an adhesive. In doing so, the joining seam is usually located parallel to the transport direction of the tube. Multi-ply tubes as required, for example, for manufacturing cement bags, can also be produced by laying several webs on top of one another before the actual tube forming. Following the tube forming, the tube is separated into tube pieces and transported away individually or preferably in stacks. A device for forming such tube pieces is disclosed, for example, in the patent specifications DE 36 40 219 C1 and DE 44 40 660 C2.
The pieces of tube produced in such a way are frequently supplied to another device, the bottom forming device, in which the former are processed further into pouches or bags. For this purpose, a bottom was molded on at least one end of a tube piece. Thus, for example, such devices for forming cross bottom valve bags are known, in which bottoms are molded even on both the ends of the tube pieces. The patent specification DE 195 49 618 C2 shows the pulling open of the ends of a tube piece. The finished bags are also regarded as tube pieces in the language used in this patent application.
Such a bottom forming device works without any disturbances especially if the tube pieces are as flat as possible. However, in practice such tube pieces are strongly corrugated especially in the region of the joining seam. This can be attributed to the fact that the joining material is not yet completely dry when leaving the tube machine. This is the case especially when using highly moisture-retaining starch-based adhesive. Therefore in the past the tube pieces were put into interim storage in a storage device before the subsequent processing. During the storage period, the tube pieces, which are frequently stored as a stack in such a storage device, are provided with a press plate so that the tube pieces assume the most planar possible position while the joining material dries off or hardens, and maintain this position even after leaving the storage device.
The laid-open specification DE 43 33 906 A1 shows such a storage device. This device comprises several tiers on which the tube pieces are stored with the help of a loading and unloading device. A press plate is assigned to every tier, with which press plate the tube pieces are compressed. The tube pieces are removed later from the tiers with the help of the loading and unloading device for the purpose of subsequent processing.
However, it has proved to be disadvantageous that the loading and unloading device, which is arranged stationarily on one side of the tiers, is required both for supplying and also for removing the tube pieces. However, this restricts the production flow and the effectiveness of the generic system since the loading and unloading device cannot supply any tube pieces when other tube pieces are being removed and vice versa.